1. Field of the Invention
The field of art to which this invention pertains is oxidation catalysts of phosphorus-vanadium-oxygen complex materials, the method of manufacturing such catalysts and the process use of those materials.
In a specified instance the catalyst contains a metal activator in addition to the phosphorus and vanadium oxygen complex generally selected from the group consisting of zinc, lithium, copper, bismuth or mixtures thereof.
2. Description of the Prior Art
U.S. Pat. No. 3,293,268 patented Dec. 20, 1966, which relates to a process for the production of maleic anhydride by oxidation of normal butane using a phosphorus-vanadium-oxygen complex catalyst produced in a specified manner.
U.S. Pat. No. 3,862,146, issued Jan. 21, 1975, relates to a process for the oxidation of butane to maleic anhydride using a phosphorus-vanadium-oxygen complex catalyst having a certain atomic ratio of phosphorus to vanadium and additionally containing the metal activator selected from the group consisting of zinc, copper, bismuth, lithium, or mixtures thereof, the metal activators also being present in a certain atomic ratio with respect to vanadium.
Belgian Pat. No. 806,475, issued Apr. 24, 1974, relates to a method of restoring the activity of a phosphorus-vanadium-oxygen metal activated catalyst which has been deactivated by the oxidation of normal butane to maleic anhydride, comprising contacting a deactivated catalyst with a reducing gas such as hydrogen, carbon monoxide, methane, hydrogen sulfide, or mixtures thereof, at a temperature of 400.degree.-600.degree. C. to reduce the vanadium from the +5 to the +4 state thereby reactivating the catalyst for a subsequent process use. The specified teachings of this patent are confined to a reactivation procedure.
U.S. Pat. No. 3,915,892, issued Oct. 28, 1975, relates to a method for the production of vanadium-phosphorus mixed oxide oxidation catalyst incorporating a very specified calcination procedure for producing a catalyst. More specifically in this patent, phase changes characterized as a dihydrate to monohydrate conversion, a monohydrate to anhydrous oxide conversion, and a post-dehydration change occur under specified procedures to effect the production of a catalyst used for the production of maleic anhydride from butane. These three bulk phase transitions as taught in the patent require that oxygen contact the catalyst during all three transitional stages. As illustrated in the examples present in this patent, a method which did not have oxygen present in a final pretreatment step produced an inferior catalyst.
Other relevant prior art may be found in the references cited against the above-described patents and in other references present in Class 260, sub-class 346.8 and/or Class 252, sub-class 435 and 437.